Medical endoscopes are inserted axially into the patient through a small orifice, incision, or other entry point, often using significant force to first expand the constriction and then overcome sliding friction between the orifice and the outer surface of the endoscope as it is advanced further. The difficulty in insertion often causes discomfort and trauma for the patient and frustration for the clinician. In many applications, the critical dimension of the orifice is smaller than the diameter of the endoscope cross-section, which means the orifice expands to accommodate the endoscope. Depending on the tissue structure, mechanical properties, and proximity to nerves, the deformation caused by insertion of the endoscope may result in tissue trauma and pain.
To reduce pain, many times the diameter of the endoscope is reduced; however, the diameter must be large enough to contain the functional components of the endoscope, and as such the diameter is often practically limited and other methods of reducing tissue trauma and pain may be developed.